Soil solution and sugar maple response to NH4NO3 additions in a base-poor northern hardwood forest of Québec, Canada

Abstract

Nitrogen additions (NH4NO3) at rates of three- and ten-fold ambient atmospheric deposition (8.5 kg ha(-1) year(-1)) were realised in an acid- and base-poor northern hardwood forest of Québec, Canada. Soil solution chemistry, foliar chemistry, crown dieback and basal area growth of sugar maple (Acer saccharum Marsh.) were measured. Except for a transitory increase of NO3 and NH4 concentrations, there was no persistent increase in their level in soil solution 3 years after N treatments, with the exception of one plot out of three, that received the highest N addition, beginning to show persistent and high NO3 concentrations after 2 years of N additions. Three years of N additions have significantly increased the N DRIS index of sugar maple but not N foliar concentration. Potassium, Ca and Mn foliar concentrations, as well as P and Ca DRIS indices, decreased in treated plots after 3 years. No treatment effect was observed for basal area growth and dieback rate. One unexpected result was the significant decrease in foliar Ca even in the treated plots that received low N rates, despite the absence of significant NO3-induced leaching of Ca. The mechanism responsible for the decrease in foliar Ca is not known. Our results, however, clearly demonstrate that increased N deposition at sites with low base saturation may affect Ca nutrition even when clear signs of N saturation are not observed.

Responses of Fine Roots and Soil N Availability to Short-Term Nitrogen Fertilization in a Broad-Leaved Korean Pine Mixed Forest in Northeastern China

“…In line with our results, Moore and Houle [46] found a significant increase in soil nitrate-N and ammonium-N after N fertilization in a northern hardwood forest in Québec. N addition experiments in coniferous and boreal forests in Sweden showed that soil nitrate-N and ammonium-N contents increased following N addition treatment [47], [48].…”

Four years of simulated N and S depositions did not cause N saturation in a mixedwood boreal forest ecosystem in the oil sands region in northern Alberta, Canada

“…Furthermore, decreasing exchangeable cation concentrations associated with soil acidification caused by N and S deposition can exacerbate nutrient imbalance such as deficiency of Mg and K for tree growth (Erisman and De Vries, 2000). Based on our results, the studied ecosystem did not show any signs of N saturation after 4 yr of N addition, which was consistent with previous research in other study sites with similar application rates (Moore and Houle, 2009;Sogn and Abrahamsen, 1998). Meanwhile, significant reduction of exchangeable cation concentrations in the mineral soil caused by N and/or S additions (Table 1) may imply potential long-term risk of nutrient imbalance in the studied boreal forest.…”

“…It is consistent with results in the accelerated N addition study in eastern Canada reporting no N saturation with deposition rates ranging from 9 to 85 kg N ha À1 yr À1 (Houle, 2006;Moore and Houle, 2009). On a long-term basis, however, 10 kg N ha À1 of deposition has been regarded as a threshold likely to lead to significant N leaching based on data from 126 forest sites in Europe and North America (Dise and Wright, 1995;Stoddard et al, 2001).…”

“…Simulated studies with elevated deposition rates have been conducted in forests less impacted by acid deposition to evaluate potential changes in ecosystem properties and processes. Simulated studies in N-limited forests could show short-term changes in the N cycle and conditions of other nutrients such as Ca and Mg uptake (Aber et al, 1998;Moore and Houle, 2009).…”

Relative role of decreasing precipitation sulfate and climate on recent lake recovery

“…Because dry S deposition is relatively low in the study area, the fact of not considering them along with annual variation of precipitation SO 4 in our analysis, should not have important impacts on our results. Deposition of inorganic N (or precipitation concentration) was not retained as an explanatory variable because N catchment budgets and experimental addition of N at forested sites located within or close to the study area [ Duchesne and Houle , 2006; Houle et al , 1997; Houle and Moore , 2008; Moore and Houle , 2009] indicated that atmospheric N is extensively retained within catchments, thereby, not affecting the acid‐base status of our lakes. The high N retention in catchments can also be deduced from low NO 3 concentration in the lakes network (see section 3.2).…”